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The nucleocapsid (N) protein is an abundant component of SARS-CoV-2 and a key analyte for lateral-flow rapid antigen tests. Here, we present new structural insights for the SARS-CoV-2 N protein using cryo-electron microscopy (EM) and molecular modeling tools. Epitope mapping based on structural data supported host-immune interactions in the C-terminal portion of the protein, while other regions revealed protein–protein interaction sites. Complementary modeling results suggested that N protein structures from known variants of concern (VOC) are nearly 100% conserved at specific antibody-binding sites. Collectively, these results suggest that rapid tests that target the nucleocapsid C-terminal domain should have similar accuracy across all VOCs. In addition, our combined structural modeling workflow may guide the design of immune therapies to counter viral processes as we plan for future variants and pandemics.

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This work presents a successful methodology to image mammalian cells adhered to nanostructured titanium by using scanning electron microscopy (SEM) operating in low‐vacuum mode following ionic liquid treatment. Human osteoblast‐like Saos‐2 cells were treated with a room‐temperature ionic liquid, 1‐ethyl‐3‐methylimidazolium tetrafluoroborate, and subsequently imaged on titanium by SEM. Titanium substrates were modified to create laser‐induced periodic surface structures (LIPSS) for visualization at the submicron scale. By using a combination of fluorescence‐based cell metabolism along with light microscopy and SEM image analysis, the shape and location of irradiated cells were confirmed to be unchanged after multiple irradiation sessions; the viability of minimally irradiated cells was also unaltered. The wet imaging conditions combined with a rapid facile protocol using ionic liquid allows this technique to fulfill a niche in examining cellular behavior on biomaterials with submicron surface features. The demonstrated method to track observed cell adhesion to submicron surface features by SEM has great implications for understanding cell migration on nanostructured surfaces as well as the exploration of simpler SEM preparation methods for cellular imaging.

Fatigue behaviour of titanium reinforced with TiB particles fabricated by ‘plasma transferred arc solid freeform fabrication’ (PTA-SFFF) technique was investigated. Rotation bending fatigue tests were conducted following the MPIF 56 standard using the staircase method approach. Experimental data is used to calculate the fatigue strength and construct S-N curves, where the results were compared to a powder metallurgy FC0205 as a benchmark material. The titanium samples were found to exhibit superior fatigue behaviour in comparison to the reference FC0205 material, performing well above 1/3 of its ultimate tensile strength with a 90% survival fatigue strength of 244 +/- 98.3 MPa versus 141 +/- 17.4 MPa. Fatigue failure mechanisms of samples were identified by examination of the fracture surfaces through scanning electron microscopy (SEM) as well as using transmission-electron microscopy (TEM) and focused ion beam (FIB) analysis techniques. Fatigue crack propagation was either arrested or deflected when propagation occurred within the vicinity of the TiB intermetallics. Fracture surfaces of the titanium matrix displayed evidence of striations while the TiB intermetallic experience cleavage fracture.

For biological imaging using electron microscopy (EM), the use of room‐temperature ionic liquids (RTILs) has been proposed as an alternative to traditional lengthy preparation methods. With their low vapor pressures and conductivity, RTILs can be applied onto hard‐to‐image soft and/or wet samples without dehydration – allowing for a more representative, hydrated state of material and opening the possibility for visualization of in situ physiological processes using conventional EM systems. However, RTILs have yet to be utilized to their full potential by microscopists and microbiologists alike. To this end, this review aims to provide a comprehensive summary of biological applications of RTILs for EM to bridge the RTIL, in situ microscopy, and biological communities. We outline future research avenues for the use of RTILs for the EM observation of biological samples, notably i) RTIL selection and optimization, ii) applications for live cell processes and iii) electron beam and ionic liquid interaction studies.

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Classically, the biomineralization field has been dominated by traditional and cryogenic electron microscopy (EM) means of characterization. While these methods work well for hypothesizing theories, observing dynamic interactions in biomimetic systems are necessary for validation. Recently, nucleation and growth processes of calcium phosphate (CaP) were revealed dynamically using novel liquid phase EM (LP-EM) [1-3]. However, limited real-time LP-EM research has considered the influence of additional biomolecules relevant to the study of hard tissues such as teeth and bone, where CaP is the primary inorganic constituent. Polyaspartic acid (pAsp) is a synthetic mimic of the soluble noncollagenous proteins found in natural mineralized collagenous tissues and is used extensively in in vitro models of collagen mineralization [4]. pAsp acts as a solution nucleation inhibitor, stabilizing CaP systems to delay solution mineralization events, thus promoting intrafibrillar collagen mineralization [4]. Other biomolecules of interest include DNA nanostructures, which can be used as templates for CaP mineralization and provide controllable self-assembled 1D, 2D, and 3D nanostructures [5].